1. Field of the Invention
This invention relates to computer display systems, and more particularly to processing overlay scan lines in computer display systems.
2. Background Information
Conventional computer systems generate pixel maps to represent graphics images. A pixel map is a two dimensional array of pixel values where each pixel value indicates information including color for a corresponding pixel on a monitor or other video display.
Video overlay is the placement of a full-motion video window on the display screen. Video overlay systems can insert a video image, such as might be generated by a television tuner, a video camera, VCR, or a video decoder, into a graphics image. Video overlay systems commonly include software that generates a pixel map, representing the graphics image and provides a video window that is filled with a color key, in the graphics image. A separate device such as a video capture card generates the video image.
Current video overlay systems use the horizontal blank time start as an indicator to start processing pixels for the next overlay scan line. This technique was sufficient with lower resolution monitors that have long horizontal blank times. Higher resolution monitors and flat panel displays, however, have significantly reduced the amount of horizontal blank time. Therefore, higher memory bandwidth is needed to ensure the pixel processing is completed in sufficient time to display the next overlay scan line.